渗氮工艺对1Gr18Ni9Ti不锈钢表面耐蚀性的影响

通过对渗氮工艺处理后1Cr18Ni9Ti钢的组织观察及力学性能测量,研究了1Cr18Ni9Ti钢的渗氮层组织及性能与渗氮温度的关系。研究结果表明:未经过渗氮处理的1Cr18Ni9Ti钢主要相成分是α-Fe相,在300℃温度下渗氮处理后的物相主要有α′N、γ′-Fe4N及ε-Fe3C相,其中γ′-Fe4N相的含量较少,在350℃和400℃温度下渗氮处理后的物相主要有α′N、γ′-Fe4N、ε-Fe3C及Cr N相。经过渗氮处理后,钢表面的硬度有明显提升,硬度值随着渗氮温度的降低而减小。在300℃温度下渗氮处理可以一定程度上提升1Cr18Ni9Ti钢的耐蚀性。     

1Cr18Ni9Ti奥氏体不锈钢的真空固溶渗氮处理

为了提高表面硬度和耐磨性,对1Cr18Ni9Ti不锈钢进行真空固溶渗氮处理。采用金相显微镜,X射线衍射仪、显微硬度计和耐磨试验机分析了渗氮层的组织与性能。结果表明,1Cr18Ni9Ti不锈钢经1 050℃真空固溶渗氮8 h后,获得了由γ′-Fe4N、CrN及含氮奥氏体组成的渗氮层;渗氮层组织致密,表面硬度为900~950 HV,有效渗层深度200μm以上;合金耐磨性得到改善,磨损失重仅为基体合金的1/26。     

2Cr13不锈钢活性屏等离子体源渗氮层组织与耐蚀性能

目的 探讨活性屏等离子体源渗氮技术提高马氏体不锈钢硬度与耐蚀性能的可行性。方法 将2Cr13马氏体不锈钢进行350～550℃、6 h活性屏等离子体源渗氮处理,采用光学显微镜（OM）、电子探针显微分析仪（EPMA）和X射线衍射仪（XRD）分析渗氮层的组织、成分和相结构,使用显微硬度计测试渗氮层的显微硬度,利用电化学腐蚀试验解析评估渗氮层的耐蚀性能。结果 经活性屏等离子体源渗氮处理后,可在马氏体不锈钢表面形成厚度为2～45μm,N原子分数为20%～25%的渗氮层,其表面显微硬度达1050～1350HV0.25,是基体硬度的4～5倍。350℃时,渗氮层以ε-Fe_2-3N相为主,且含有少量αN相;450℃时,渗氮层由αN、ε-Fe_2-3N和γ’-Fe₄N相构成;渗氮温度升至550℃时,渗氮层由α-Fe、CrN和γ’-Fe4N相构成,αN、ε-Fe2-3N相消失。350、450℃时,渗氮层在3.5%NaCl溶液中的阳极极化曲线出现明显钝化区,而未渗氮的2Cr13不锈钢并未发现钝化区,自腐蚀电位E_corr由未渗...     

低温渗氮对水泵用0Cr13Ni4Mo钢表面改性研究

为提高马氏体不锈钢0Cr13Ni4Mo的耐磨性,对水泵叶片进行表面处理,具体为分别在450℃、480℃和510℃对其进行2 h的盐浴渗氮。使用显微硬度计、XRD衍射仪、光镜、电化学工作站、摩擦磨损试验机及SEM等设备,研究了渗氮温度对0Cr13Ni4Mo钢的表面物相、硬度、渗层显微形貌、耐蚀性以及耐磨性的影响。结果显示:随着渗氮温度升高,物相由氮原子在马氏体中的过饱和固溶体α'N转变为Cr N和γ'相,材料点蚀电位下降,同时表面硬度增加,510℃处理后可达HV 1 200,渗层厚度为20μm,Cr N相大量析出,点蚀电位下降360 m V,磨损体积为未渗氮样品的17.6%,减磨效果明显。     

离子渗氮AISI 420马氏体不锈钢耐蚀行为研究

采用不同温度对AISI 420马氏体不锈钢进行离子渗氮处理.借助光学显微镜和X射线衍射(XRD)技术分析了渗氮层的微观组织结构,利用显微硬度计测试了渗氮层的硬度分布,通过电化学极化曲线测试和盐雾腐蚀试验研究了离子渗氮AISI 420不锈钢在模拟工业环境中的腐蚀行为.结果表明:AISI 420不锈钢350℃低温离子渗氮层由ε-Fe3N和N过饱和固溶体αN相组成,其化学稳定性高,加之固溶Cr元素的联合作用,明显提高了AISI 420不锈钢基材的腐蚀抗力.AISI 420钢经450℃和550℃渗氮处理,渗氮层中的αN分解成了α相和CrN,造成基体贫Cr,降低了基材的耐蚀性能.马氏体不锈钢低温离子渗氮处理不仅可以提高表面硬度,而且可以获得良好的耐蚀性能.     

Cu的时效行为及其对0Cr14Ni5Mo2Cu2Nb钢性能的影响

研究了不同时效温度下的沉淀硬化不锈钢0Cr14Ni5Mo2Cu2Nb的TEM组织、硬度和冲击韧性.结果表明:时效过程中,0Cr14Ni5Mo2Cu2N钢主要以ε-Cu相析出为主.时效温度为420℃时,Cu以细小共格ε-Cu相析出,导致0Cr14Ni5Mo2Cu2N钢的硬度达到峰值,而韧性最差,冲击断口以解理为主.随着时效温度增加,ε-Cu相逐步脱溶长大,基体再结晶,硬化程度逐步降低,韧性升高,冲击断口逐步过渡为全韧窝形貌.0Cr14Ni5Mo2Cu2Nb钢的韧性主要决定于冲击裂纹扩展功.时效组织对0Cr14Ni5Mo2Cu2Nb钢冲击裂纹形成功影响较小,对裂纹扩展功有着较大影响.     

离子渗氮马氏体不锈钢的微观组织与腐蚀行为

采用扫描电镜、X射线衍射(XRD)、极化曲线和显微硬度等方法研究表面离子渗氮X12Cr13马氏体不锈钢的渗氮层成分、显微组织结构、硬度以及腐蚀性能。结果表明:离子渗氮马氏体不锈钢表面形成了70μm的渗氮层,渗氮层由化合物层和扩散层组成,化合物层的组成相主要为γ-Fe N和ε-Fe N。离子渗氮不锈钢经过72 h纯水浸泡后表面发生点蚀。基体内部向表层的扩散降低了钢中的固溶铬含量以及渗氮层形成的孔隙和裂纹共同降低马氏体不锈钢的耐腐蚀性。     

Cu的时效行为及其对0Cr14Ni5Mo2Cu2Nb钢性能的影响

研究了不同时效温度下的沉淀硬化不锈钢0Cr14Ni5Mo2Cu2Nb的TEM组织、硬度和冲击韧性.结果表明时效过程中,0Cr14Ni5Mo2Cu2N钢主要以ε-Cu相析出为主.时效温度为420℃时,Cu以细小共格ε-Cu相析出,导致0Cr14Ni5Mo2Cu2N钢的硬度达到峰值,而韧性最差,冲击断口以解理为主.随着时效温度增加,ε-Cu相逐步脱溶长大,基体再结晶,硬化程度逐步降低,韧性升高,冲击断口逐步过渡为全韧窝形貌.0Cr14Ni5Mo2Cu2Nb钢的韧性主要决定于冲击裂纹扩展功.时效组织对0Cr14Ni5Mo2Cu2Nb钢冲击裂纹形成功影响较小,对裂纹扩展功有着较大影响.     

电弧等离子体辅助渗氮处理Cr12MoV钢的组织结构及硬度

采用不同温度对Crl2MoV钢进行电弧等离子体辅助渗氮处理.采用X射线衍射(XRD)分析渗氮层的相组成,采用扫描电子显微镜(SEM)及光学显微镜分别观察渗氮样品表面形貌及横截面形貌,利用显微硬度计测试渗氮层的硬度分布.结果表明:实验钢渗氮层的结构由CrN+γ'-Fe4N+ε-Fe3N的化合物层及由含氮马氏体相α-Fe (N)组成,渗氮层的厚度随处理温度的升高而增加.渗氮处理后能明显提高Cr12MoV钢基体的显微硬度.     

马氏体不锈钢不同渗氮方法对比试验

采用离子渗氮、液体渗氮及气体渗氮对耐蚀耐热马氏体型热稳定不锈钢1Cr12Ni2WMoVNb进行表面改性,研究了不同渗氮方法下不锈钢的硬度、组织形貌、物相变化及脆性,并对3种渗氮方法下不锈钢的耐蚀性及耐高温磨损性能进行了比较。结果表明:3种渗氮方法均可大幅度提高不锈钢的表面硬度,且不同渗氮处理后不锈钢的渗层组织结构大致相同,但表面物相有所差异,离子渗氮后的表面物相主要为Fe₄N及少量CrN相,液体渗氮后为Fe₃O₄及ε相,气体渗氮后为Fe₃O₄、Fe₄N及少量ε相;3种渗氮方法均可提高不锈钢的耐磨损性能,特别是在500~600 ℃下的高温耐磨性得到了大幅提升,但不锈钢渗氮后的耐蚀性均有所降低。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。